Opalinuston Formation (Zillhausen Member)

Bed no.

1. [Zopfplatten] (ca. 1.0 m [Rieber 1963]).
2. (ca. 8.0 m [Rieber 1963]): claystone with layers of siderite concretions (only the uppermost 2 m are exposed) at 0.4 m, 0.9 m and 1.5 m below the top.

Achdorf Formation

1. (0.15–0.2 m): grey, hard marly limestone, with bivalves and Leioceras crassicostatum.
2. (0.15 m): grey carbonaceous marlstone; in the upper part gritty, with siderite concretions.
3. (0.03 m): grey, very hard marly limestone nodules.
4. (0.2 m): grey marlstone with compressed Leioceras crassicostatum.
5. (0.05 m): light grey, pyritic marly limestone nodules with dark grey Chondrites burrows. Mainly small specimens of Leioceras “ comptum”, irregularly embedded and partly accumulated.
6. (0.4 m): carbonaceous marlstone with higher clay content than in beds 4 and 6.
7. (0.03 m): grey marly limestone nodules.
8. (0.2 m): clay marlstone.
9. (0.18 m): marly limestone, partially splitting in the lower third. At the base with hazelnut-sized pebbles. Above very hard marly limestone concretions with shrinkage cracks (septaria) and fine shell debris.
10. (ca. 2.0 m): claystone, badly exposed.
11. (0.05 m): grey, hard marly limestone.
12. (ca. 5.5 m): claystone with layers of septaria und siderite concretions (section is divided by a wooden bridge at the “Geopfad” into a lower and an upper part) below: ca. 4.0 m claystone with a layer of septaria (0.05 m) ca. 1.8 m above the base above: ca. 1.5 m claystone (with layers of siderite concretions at 1.1 m, 0.8 m, 0.7 m and 0.4 m below the top; ca. 0.85 m below the top, a hard, sandy, micaceous marly limestone with ichnofossils; 0.25 m below the top another septaria layer).
13. (0.05 m): hard carbonaceous marlstone.
14. (0.2 m): greyish brown marly limestone with Ludwigia murchisonae (see Rieber 1963).
15. (0.4–0.45 m): grey carbonaceous marlstone.
16. (0.25 m): greyish brown, marly limestone.
17. (0.15 m): carbonaceous claystone.
18. (0.25 m): grey, hard marly limestone; with Staufenia staufensis and Brasilia bradfordensis (Rieber 1963). This is the top layer of the small waterfall.
19. (0–0.12 m): grey, very hard, loaf-shaped marly limestone nodules with Staufenia staufensis (SMNS 70519/1 [microconch]). From a corresponding nodule layer of the nearby Bezighofenbach section (Rieber 1963), a large S. cf. (SMNS 70519/55) with a relatively wide umbilicus was recorded.
20. (ca. 1.7 m): grey marlstone, mostly not exposed. (Rieber (1963) described 4 harder beds up to 1.65 m above bed 20, the uppermost one as an oolitic nodule layer with Staufenia staufensis).
21. (ca. 6 m): claystone, not exposed; only the uppermost 0.3 m are visible.
22. (0.05–0.15 m): [Inopernabank] spotty-grey, tough, marly limestone with greyish brown bark and isolated small, rounded pebbles. At the base larger Thalassinoides burrows, in the lower part of the bed small, flattened marlstone pebbles (0.03–0.05 m). Few fossils: Gryphaea sp., Pinna sp., belemnites.
23. (6.0 m): dark claystone with several layers of siderite concretions in the upper 0.5 m.
24. (0.05–0.1 m) [Konglomeratbank (= bed 3 in Dietze et al. 2019)] : grey marly limestone with abundant pebbles. Ludwigella arcitenens (Fig. 16: 3a, b).
25. (ca. 0.3 m): dark grey, laminated carbonaceous claystone, with fine shell debris and small nodules (up to 5 mm). Rare, compressed Graphoceras sp., a fragmentary Graphoceras sp. (SMNS 70519/2) at the top sample Ro19-1: 0–0.05 m above the Konglomeratbank sample Ro19-2. 0.25–0.3 m above the Konglomeratbank
26. (max. 0.1 m) [Calceolabank (= bed 5 in Dietze et al. 2019)] : grey, marly limestone with many Gryphaea calceola in its lower part, in clay-rich parts predominantly in "convex upward" position. Some of the shells are stacked into each other. The layer is nodular in some places and then wedges out. At one point many large Trigonia alemanica and compressed ammonites (? Graphoceras) occur. At another place nearby well-preserved Graphoceras cf. concavum (Fig. 16: 1, 4) and Brasilia cf. decipiformis (Fig. 21: 2a, b, 5a, b).
27. (0.15 m): carbonaceous claystone with few small gryphaeids.
28. (0.1–0.15 m): carbonaceous claystone with masses of small gryphaeids (Gryphaea calceola) up to 2 cm in diameter and small phosphorite concretions. Sample Ro19-3
29. (0.15 m): grey calcoolitic marlstone (reddish brown in weathered state), with single hard marly limestone nodules. Few bivalves and belemnites.
30. (0.15 m) [Rostrote Kalkbank (= bed 9 in Dietze et al. 2019)]: hard limestone, rusty red crust, inside greenish grey and brown-red marbled.
31. (0.95 m; see Ohmert 2004): carbonaceous claystone. Sample Ro19-4: 0–0.05 m above the Rostrote Kalkbank Sample Ro19-5: 0.05–0.15 m above the Rostrote Kalkbank

Wedelsandstein Formation

34–36. [Sowerbyi-Oolith (= beds 11–13 in Dietze et al. 2019)] (see Franz 1986, Dietze et al. 2019).

1. (0.05–0.07 m): limestone nodules, calcitic ooids only in Chondrites burrows.
2. (0.06–0.1 m): dark grey, muscovite-bearing, laminated oolitic claystone with belemnites and Hyperlioceras.
3. (0.04–0.13 m): grey elongated limestone nodules with irregular surfaces, hard, calcitic oolites (0.1–0.2 mm diameter), with small pebbles, in places densely packed. Bivalves (Gryphaea, Entolium), belemnites, serpulids; strongly bioturbated (Chondrites). Ammonites: Hyperlioceras sp. and Euhoploceras sp. (see Dietze et al. 2019).

Higher up Unterer Wedelsandstein (see Dietze et al. 2019).

Landslide above the former Friedrichstal castle near Hechingen-Boll

Achdorf Formation

Bed no. / sample no.

1. (min. 1.5 m): claystone, thickness unknown. Only uppermost part exposed.
2. (0–01.15 m): nodular bed of grey marly limestone, with small light grey, phosphoritic pebbles (0.2–1 cm) and marly limestone pebbles up to 3 cm, partly compressed. Graphoceras sp.
3. (1.5 m): dark grey claystone
4. (0.15 m): nodular bed, like bed 2, but continuously developed.
5. (ca. 4 m): grey claystone

• not exposed
• Slipped blocks from the Rostrote Kalkbank (0.15 m) and the Calceolabank (0.15 m) with Gryphaea calceola, Graphoceras sp. (SMNS 70519/3), Euaptetoceras sp. (SMNS 70519/4).

1. (ca 7–8 m): claystone, mostly badly exposed. The upper 3 m excavated for sampling. Layers of siderite concretions at 0.15 m, 0.2 m, 0.5 m and 1.5 m below top. 1.6 m below top 0.10–0.15 cm long and 0.03–0.04 m thick lenses of light grey, lenticularly bedded, fine-sandy limestones.

• Ha19-1 (3.05–2.55 m below bed 7)
• Ha19-2 (2.05–1.55 m below bed 7)
• Ha19-3 (1.05–0.25 m below bed 7)
• Ha19-4 (0.15–0.25 m below bed 7)

1. (0.15 m) [Sowerbyi-Oolith]: claystone, with occasional irregular-shaped, often flat nodules (up to 0.10 m long and 0.04 m thick) of greyish limestone with borings, the sediment infill of which is calcoolitic. The nodules are settled on all sides with bryozoans, oysters and serpulids and show in places a fine, dark brown coating. Small phosphoritic pebbles (up to 0.05 m) are not rare. Some of them show parallel scratch-like traces. In the pebbles occasionally casts of endobenthic bivalves occur. In the claystone fragments of Actinostreon, Ctenostreon and fragments of abraded belemnites with borings occur. One fragmentary Hyperlioceras from the “Weinhalde” section, 700 m SE of the Hausterberg section.

• Ha19-5 / (above bed 7)

1. (0.15 m): sandy marly limestone with separation joints. Large Thalassinoides burrows at the base; Zoophycos.
2. (0.3 m): marly claystone; at the base sandy, at the top silty.

• Ha19-6

2.3.1 Mühlbächle

Achdorf-Formation:

Bed no. / sample no.

1. (min. 0.5 m): claystone
2. (0.1–0.12 m): pyrite-bearing grey, weathered rusty, hard marly limestone. Many tiny gryphaeids, rare belemnites and bivalves. Few, mostly very small ammonites. Brasilia bradfordensis (Fig. 19: 1a, b)
3. (0.45 m): claystone. In the upper part a single carbonaceous burrow (diameter up to 0.04 m) was observed.
4. (0.05–0.1 m): hard, grey marly limestone with many pebbles of different size and burrows at the base.
5. (1.8–2.0 m): claystone; only partly exposed.
6. (0.05–0.08 m): grey marly limestone with pebbles; accumulations of very small gryphaeids.
7. (1.6 m): claystone with several layers of siderite concretions (0.4, 0.6, 0.8, 0.9, 1.0, 1.15 and 1.3 m above base).
8. (0.05–0.08 m) flat to nodular, hard, grey marly limestone with occasional pebbles.
9. (0.01–0.05 m): marlstone.
10. (0.15–0.18 m): [Inopernabank] greyish brown, hard marly limestone, easily splitting in weathered state. Numerous larger pebbles, especially in the lower part, where they can be flattened. Small, light grey pebbles give the rock a speckled appearance. Large burrows at the base. Bivalves are characteristic for the Inopernabank (big Pholadomya, Inoperna sowerbyana, Gryphaea calceola [smaller ones than those in the Calceolabank]). Some of the endobenthic bivalves are still in life position (see Quenstedt 1857: 357).
11. (ca. 3.5–4.0 m) claystone, not exposed.
12. (0.1–0.12 m) [Konglomeratbank]: hard, greyish brown marly limestone, with big pebbles. Large Pholadomya in life position.
13. (0.35 m): grey marl with abundant Gryphaea calceola (up to 0.03 m).
14. (0.15–0.18 m) [Calceolabank] (= bed 12 in Dietze et al. 2019): Hard, grey, pyrite-bearing marly limestone. Partly easily splitting. Weathered brown and decomposing. At the base abundant Gryphaea calceola (up to 0.06 m large), only very rarely with right valves. The gryphaeids are embedded individually or in accumulations. Well-preserved ammonites are relatively common, predominantly in the lower third of the bed: Brasilia cf. decipiens (Fig. 19: 5a, b), B.aff.decipiens (Fig. 20: 3a, b), Graphoceras aff. magnum (Fig. 20: 1a, b), G. cavatum (Fig. 21: 2a, b), G.cf.cavatum (Fig. 20: 2a, b; Fig. 21: 1a, b), G. pulchrum (Fig. 22: 3a, b), G. decorum (Fig. 22: 1a, b), G. formosum (Fig. 22: 2a, b, 5a, b), G. fallax (Fig. 22: 4), Ludwigella cornu (Fig. 19: 2), L. attracta (Fig. 19: 3), L. micra (Fig. 19: 4), Euaptetoceras cf. euaptetum (Fig. 23: 1a–c), E.cf.kochi (Prinz) (The ammonite figured in Fig. 24 comes from an excavation pit in Jungingen 500 m west of the Mühlbächle stream).
15. (0.20 m): grey carbonaceous claystone.
16. (0.05 m): single hard marly limestone nodules (up to 0.05 m).
17. (0.20 m): grey carbonaceous claystone with small phosphoritic nodules. Masses of small gryphaeids (Gryphaea calceola).
18. (0.10 m): rough, phacoidal, reddish marlstone with occasional hard marly limestone nodules; pholadomyids. Graphoceras concavum is recorded from the Bachenau section (Rieber 1922, 1963), which is situated about 50 m east of the Mühlbächle.
19. (0.08–0.1 m): light grey, very hard limestone with numerous dark grey burrows (Chondrites and cylindrical burrows up to 4 mm in diameter). Occasional compressed ammonites. Thin marly joint with bed 20.
20. (0.1–0.12 m) [Rostrote Kalkbank] (= bed 15 in Dietze et al. 2019): On the outer surface weathered with a typical rusty red margin. In fresh state a hard, light grey, reddish and greenish grey marbled limestone. Graphoceras sp.
21. (8.0 m) (= bed 16 in Dietze et al. 2019): claystone (thickness according to A. Rieber 1922). Poorly exposed.

• Mue19-1

Wedelsandstein-Formation:

1. (0.15–0.2 m) [Sowerbyi-Oolith] (= bed 17 in Dietze et al. 2019): grey carbonaceous claystone with marly limestone nodules. Some nodules show concentric growth structures. Club-shaped borings are filled with calcitic oolites. The surface of rounded to flat nodules is densely covered on all sides with bryozoans, serpulids and sessile foraminifers. Some other nodules are grey inside, calcoolitic, with scattered very small light grey pebbles. Rare serpulids, belemnites, bivalves and pebbles occur in the matrix. The very irregular-shaped, calcoolitic limestone nodules are overgrown as well. In the claystone between the nodules occasional belemnites and endobenthic bivalves, Entolium.

Higher up follows the Unterer Wedelsandstein (see Dietze et. al. 2019).

2.3.2 Starzel (river bed near the road Jungingen–Killer, see Lörcher (1939: 224):

Achdorf-Formation:

bed no.

1. (min. 0.4 m): claystone
2. (0.05 m): grey, flat nodular marly limestone.
3. (0.01–0.05 m): marly joint.
4. (0.15–0.2 m) [Inopernabank]: hard, grey limestone, in places speckled with small, light grey pebbles and large burrows at the base. Larger, mostly flattened pebbles occur predominantly in the lower part of the bed. The bed varies greatly in thickness and compactness. Large Pholadomya lirata, Inoperna sowerbyana, Goniomya literata, Gryphaea calceola (up to 0.03 m), Entolium sp., Propeamussium pumilum, and Oxytoma inaequivalvis. Small gastropods, belemnites and ammonites. Graphoceras cavatum (Fig. 13: 2a, b, 9a, b), G.aff.fallax (Fig. 13: 3), Brasilia decipiens (Fig. 13: 1a, b), Ludwigella attracta (Fig. 13: 7, 8), L. tenuis (Fig. 13: 4), L.aff.tenuis (Fig. 13: 5), L. attenuata (Fig. 13: 6), Planammatoceras sp. (Fig. 14: 1a–c). Lörcher (1939: 224) misidentified this bed as Calceolabank).
5. (min. 0.5 m): claystone.
6. Higher parts of the section are not exposed, except of the Rostrote Kalkbank bed above the railway bridge near the village Killer.

2.4.1 Heiligenbach

(the strata below bed 1 were not studied in detail)

Bed no. / sample no.

“Ob -1m“ He19-1 1.0 m below Onkoidbank.

“Ob“ (0.15–0.2 m) [Onkoidbank]: L. opalinum [m], about 11 m below “Wasserfallschichten”. In its upper part a marly limestone, dark grey, upper and lower surface very irregular, with shrinkage cracks and oncoids (Fig. 3).

“x” (about 11 m): sandy, carbonaceous claystone, a single Lytoceras dilucidum.

• He19-2 0–0.1 m above Onkoidbank: numerous crinoids and bivalves.
• He19-3 1 m above Onkoidbank, numerous crinoids, Leioceras opaliniforme (body chamber).
• He19-4 2 m above Onkoidbank.
• He19-5 5 m below “Wasserfallschichten”: Isolated lenticular, thin-layered, sandy-calcareous layers, micaceous, with crinoid debris (Pentacrinitenplatte with Chariocrinus wuerttembergicus), ichnofossils (Gyrochorte, Palaeophycus and others).
• He19-6 3 m below “Wasserfallschichten”

“WS” (about 14–15 m) [Wasserfallschichten]: with several cascades in the river bed (Rieber 1922; Lörcher 1939; Kobler 1972: 14, pl. 2 [left column]).

1. (2.0 m): claystone, dark grey (at approx. 1.0 ca. 0.04 m irregular carbonaceous marlstone pebbles.

• He19-7 (middle)

1. (0.08–0.1 m) [Belemnitenbreccie]: hard, bluish-grey marly limestone, base very irregular; with a coquina of bivalves/echinoderms and grey pebbles, partially with bivalve borings, irregularly bedded. Abundant belemnites, Gryphaea calceola, Chlamys textoria.
2. (7–8 m): claystone with layers of siderite concretions; only partly exposed.

• 3a: 1.0 m above bed 2: layer of nodules (carbonaceous marlstone/siderite)

• He19-8
• He19-9 (3.0 m above bed 2): rare bivalves, Bactryllium, cylindrical burrows.
• 3b: ca. 4.0 m above bed 2: noticeable nodule layer (brown marly limestone)

• He19-10 (1.0 m below top): burrows

In the upper 0.25 m single mica-bearing fine sandy limestone plates (up to approx. 0.03 m thick) with a rich ichnofauna, Gyrochorte comosa.

1. (0.7 m) [Zopfplatten]: fine sandy limestone, mica-bearing, splitting into thin plates; Gyrochorte comosa.
2. (ca. 3.5 m): very poorly exposed

• 1.5 m above bed 4: claystone with siderite nodules.

• He19-11 small gastropods.
• He19-12 (directly below bed 6): very numerous agglutinating foraminifera.

1. (0.15–0.2 m): grey, marly limestone, small pebbles (up to nut-size). Lörcher (1939) described ammonites probably coming from this bed (or from bed 10).
2. (ca. 0.1 m): dark grey claystone.
3. (0.05 m): grey marly limestone, few small pebbles.
4. (ca. 3–4 m): dark grey claystone, very badly exposed

• He19-13 (middle)

1. (0.01 m): grey carbonaceous marl with a layer of pebbles.
2. (0.4 m): dark grey claystone.
3. (0.3 m): grey marlstone.
4. 0–10 cm grey, lenticular to nodular marly limestone; accumulations of remarkably small sized ammonites: Leioceras “ comptum”, L. evolutum, L. striatum, L. paucicostatum (from the corresponding layer of the Steinlach creek north of Mössingen-Talheim: L. crassicostatum, L. “comptum”, L. striatum, L. paucicostatum, L. evolutum, L. sp. (with broad whorls)), occasional bivalves; shrinkage cracks.
5. (0.03 m) dark grey marly claystone.
6. (0–0.1 m): carbonaceous marl nodules, in places a continuous, very hard carbonaceous marlstone bed with calcite-filled shrinkage cracks (Septarienbank). Occasional small ammonites (Leioceras “ comptum”).
7. (0.02 m) (directly on top of bed 15): sandy carbonaceous marl tiles, trace fossils (not continuously present).
8. (0.35 m): dark grey marly claystone.
9. (0.08 m): grey sandy carbonaceous marlstone.
10. (0.65 m): dark grey claystone with siderite nodules.

• He19-14

1. (0.05–0.08 m): dark grey carbonaceous marl with small pebbles; thin marly claystone layer.
2. (0.1–0.12 m): grey carbonaceous marl with small pebbles [20 + 21: “Doppelbank”]
3. (ca. 2 m): dark grey claystone with grey limestone lenses.

• He19-15 agglutinating foraminifera

1. (0.05–0.07 m): grey carbonaceous marl, irregular surface; abundant pyrite, pebbles up to 0.03 m.
2. (ca. 1 m): dark grey claystone, approx. 0.7 m above bed 23 with a layer of siderite nodules.
3. (0.05 m): grey marly limestone with small pebbles.
4. (1.3 m): dark grey claystone, layers of siderite nodules at 0.15, 0.65, and 1.15 m above bed 25.

• He19-16 (0.01 m above bed 25): crinoids

1. (0.08 –0.1 m): brown, coarsely conglomeratic marly limestone; bivalves and belemnites.
2. (3.5–4 m): dark grey claystone, only partly exposed.

• He19-17(0.25 m below bed 29)

1. (0.15 m): grey lenticular splitting carbonaceous marl.
2. (0.15 m): light grey marly limestone with dark grey spots.
3. (0.03 m): brownish grey carbonaceous marlstone with masses of small pebbles.
4. (0.15 m): brown marly limestone with bivalves [29–32: Staufensisbank]
5. (ca. 6 m): claystone, not exposed; according to Lörcher (1939) with several carbonaceous beds.

• He19-18 (0.5 m above bed 32)
• He19-19 (0.2 m below bed 34)

1. (0.1–0.15 m): grey marly limestone, thin bivalve shells; single small pebbles.
2. (2 m): claystone.

• He19-20 (0.4 m below bed 36)

1. (0.01 m): grey marly limestone, small pebbles up to 3 cm; shell debris. Belemnite, nautiloid (Cenoceras), Graphoceras.
2. (ca. 0.7 m): dark grey claystone.
3. (0.05 m): irregularly shaped bed of grey marly limestone.
4. (0.7 m): claystone; 0.4 m above bed 38 a layer of siderite nodules. Arthropod burrows at the top.

• He19-21 (0.4 m above bed 38)

1. (0.1 m) [Inopernabank]: grey, coarse conglomeratic limestone, with phosphoritic spots; Pholadomya lirata, Gryphaea calceola, Inoperna sowerbyana, ammonites: Graphoceras cf. caduciferum (Fig. 17: 1a, b), ? Brasilia sp. (SMNS 70519/54).
2. (4 m) (= bed 1 in Dietze et al. 2019): dark grey claystone, occasional flat siderite nodules at 0.6 m below top.

• He19-22 (41 middle)
• He19-23 (41, 0.5 m below bed 42)

1. (0.08–0.1 m) [Konglomeratbank ] (= bed 2 in Dietze et al. 2019; starting from here this section had already been sampled in 1988): blueish grey limestone with pebbles. A fragment of Graphoceras sp. (Fig. 17: 2).
2. (0.02 m): calcoolitic marl.

• He19-24

1. (0.15–0.17 m): grey to brownish marly claystone.

• He19-25

1. (0.17 m) [Calceolabank]: (= bed 5 in Dietze et al. 2019) grey marly limestone, lenticular splitting, on top 0.02 m oolitic marl. Thin-shelled bivalves, at the base (in places in marl lenses) abundant Gryphaea calceola. Ammonites: Brasilia decipiens (Fig. 18: 1), B. aff. decipiens (Fig. 18: 4a, b). Graphoceras fallax (Fig. 18: 5), G. cavatum (Fig. 18: 2), G. cf. v-scriptum (Fig. 18: 3), Ludwigella arcitenens (Fig. 17: 3), L. sp. (Fig. 17: 5), Euaptetoceras infernense sensu Buckman (Fig. 17: 4).
2. (0.02 m): greyish beige claystone.

• He19-26

1. (0.05 m): single grey limestone nodules up to 5 cm, partly with numerous small Gryphaea and serpulids.
2. (0.33 m): grey laminated claystone, with abundant small gryphaeids, single belemnite.

• He19-27 (at the base)
• He19-28 (0.1 m above bed 47)

1. (0.25–0.35 m) [Rostrote Kalkbank] (= bed 9 in Dietze et al. 2019): reddish brown carbonaceous marl with marly limestone nodules; 2 or 3 layers of flat siderite nodules. At the base 0.05 m greenish brown marly limestone.

This outcrop is covered by terrace gravel of the Heiligenbach.

2.4.2 Eastern tributary of the Heiligenbach coming from the Sießenwald, approx. 30 m east of the “Hunnengrab”

In the river bed there is a light grey, hard limestone bed (0.15 m) with a rust-coloured rim and many burrows. Its lithology resembles the lower bed of the Rostrote Kalkbank from the Mühlbächle section at Jungingen. An indeterminable ammonite fragment. A larger Euaptetoceras sp. (SMNS 70519/5) comes from a loose block of the Rostrote Kalkbank.

2.4.3 Hanneswiesle

This outcrop is located on a forest path in the Hanneswiesle district west of Beuren.

Bed no.

1. (0.08–0.1 m) [Konglomeratbank].
2. (0.2 m): carbonaceous claystone.
3. (0.03 m): firm marlstone with many Gryphaea calceola.
4. (0.15–0.2 m) [Calceolabank]: brownish marly limestone, splitting into plates in places, but in places solid grey marly limestone with a reddish brown rim also in weathered state. Small gryphaeids are firmly fixed in clusters on the bed surface (see Erb 1938). Ammonites (Graphoceras pulchrum (Fig. 15: 5a, b), G. cf. pulchrum (Fig. 15: 4a, b), G. cf. concavum (Fig. 15: 1a, b), G. decorum (Fig. 15: 2), G. aff. apertum (Fig. 15: 3a, b), Ludwigella arcitenens (Fig. 15: 6a, b), Euaptetoceras infernense sensu Buckman (Fig. 14: 2a, b)) are mainly found in the lower part of the bed.

Since we did not find Aalenian ammonites in this outcrop, we here refer to Dietze et al. (2019) for the description of the section.

For the present study, a total of 41 samples were taken in September 2018 and September 2019. Individual samples, which were already taken in 1988 at the Heiligenbach, were included in the investigation.

Microfossils have been extracted by first drying the samples (0.5–1 kg), breaking them down with the aid of hydrogen peroxide (3% solution of H₂O₂) and then sieving them under water. The residues were then cleaned by boiling them for 15 minutes in a moderately concentrated sodium chloride solution (3 teaspoons NaCl / 0.25 l water). From the fractions > 0.5 mm and > 0.315 mm of the residues, 3–5 trays were examined. From the fractions > 0.2 mm and > 0.15 mm we examined 3 trays.

Photographs were taken using SEM in Stuttgart (SMNS).

The ammonite fauna of the Upper Aalenian of SW Germany is dominated by members of the subfamily Graphoceratinae Buckman, 1905, besides rare Hammatoceratinae Buckman, 1887. The Graphoceratinae originate in the subfamily Leioceratinae Spath, 1936. The family Graphoceratidae itself descends from the Upper Toarcian genus Pleydellia Buckman, 1899 (Grammoceratinae Buckman, 1905 within the family Hildoceratidae Hyatt, 1867) (Chandler 1997; Chandler et al. 2012, Howarth 2013).

The evolution within the Graphoceratidae occurred in a chronocline ranging from the lowermost Aalenian (Opalinum Zone, Opalinum Subzone) to the lowermost Bajocian (Discites Zone), with an immense morphological variability within each of the temporally succeeding faunas. In this plexus, individual morphologies sometimes have a long temporal range, whereas the variability of the succeeding faunas as a whole shifts – that is the reason why we can distinguish and define faunal biohorizons. Faunal biohorizons reflect the change of variation in the course of evolution of ammonites, here of Graphoceratidae (e.g., Chandler 1997, 2019; Chandler and Callomon 2009; Dietze et al. 2014, 2017). There is a gradual change from one genus to the next, so that we can – e.g., in the case of the ammonites under study here – find Graphoceras morphologies together with Brasilia morphologies coeval in a single bed, accompanied by specimens showing a mixture of characters of both morphogenera. For a slightly older (Bradfordensis Zone, Gigantea Subzone) overlap of the morphogenera Brasilia and Graphoceras (with a variability of the whole fauna closer to Brasilia) see Dietze et al. 2014 (ammonites therein were there described as chronospecies). An intersection of Ludwiga and Brasilia can be seen in the top of the Staufensisbank of the nearby Plettenberg/Hausen am Tann (Western Swabian Alb) sections (Dietze et al. 2017b; fauna described morphospecifically). Chandler (1997) demonstrated convincingly the evolution of the Graphoceratidae and the intersection of the nominal morphogenera in the Aalenian of Horn Park Quarry near Beaminster (Dorset, SW England).

In the literature, there are many attempts to classify the plexus of the Graphoceratidae into categories (families, subfamilies, morphogenera, morphospecies). The results of these attempts and the erection of new genera and species depended often by chance, depending on where the author had material from, often without any accurate stratigraphy. The great number of genera and species described in the literature (e.g. Buckman 1887–1907; Horn 1909; Hoffmann 1913; Althoff 1940; Rieber 1963; Géczy 1967; Contini 1969; Ureta Gil 1983; Henriques 1992; Chandler 1997; Howarth 2013) does by no means reflect the number of monophyletic genera and biological species, which was in fact much smaller (Chandler and Callomon 2009). These authors demonstrated the variation of a palaeobiospecies of the Leioceratinae, Leioceras comptocostosum, within one timeslice of the Scissum Zone (Lower Aalenian).

We here determined the ammonites conventionally as morphogenera and morphospecies, since we do not have enough material to describe these ammonites chrono- or (palaeo)biospecifically. However, it is most likely that all graphoceratid ammonites from the cavatum horizon described here represent a single palaeobiospecies.

4.2.1 Family Graphoceratidae Buckman, 1905, Subfamilies Leioceratinae Spath, 1936 and Graphoceratinae Buckman, 1905

Leioceras opalinum [m] and L. opaliniforme [M] occur about 10 m below the “Wasserfallschichten” in the Heiligenbach creek.

The ammonites from the “Comptum” Subzone are represented by L. “comptum”, L. crassicostatum, L. evolutum, L. paucicostatum and L. striatum. They are significantly smaller than the L. “comptum” faunas from the Wochenberg and Gosheim (western Swabian Alb) which comprise more evolute morphs. These ammonites will be described later in detail.

A single Brasilia bradfordensis (Fig. 19: 1a, b) of the Bradfordensis Zone (Bradfordensis Subzone) was recovered from bed 2 of the Heiligenbach section.

The graphoceratid fauna of the Inopernabank (Bradfordensis Zone, Gigantea Subzone) and from the Konglomeratbank to the Rostrote Kalkbank (Concavum Zone, Concavum Subzone) is characterized by the predominance of the morphogenus Graphoceras; less common are representatives of the morphogenus Brasilia and a substantial number of ammonites with various combinations of both morphogenera (cf. Rieber 1922: 47, 51). In the slightly older decipiformis horizon of the Gigantea Subzone (Bradfordensis Zone, see Fig. 26) ammonites of the genus Brasilia exhibit larger-sized and smooth shells, with generally broader whorl sections and a wider umbilicus compared to Graphoceras (Chandler 1997; Dietze et al. 2014). The ammonites determined as B. decipiens (Fig. 13: 1a, b, Fig. 18: 1), B. aff. decipiens (Fig. 20: 3a, b) and B. cf. decipiformis (Fig. 16: 2a, b, 5a, b) are very similar to examples of the genus Brasilia from the Bradfordensis Zone (Gigantea Subzone, decipiformis horizon) of Geisingen (SW Germany) and Dorset (SW England) (Dietze et al. 2014; Buckman 1887–1907; Chandler 1997). Some of the studied ammonites show mixed characters and are obviously intermediates between Brasilia and Graphoceras: B. aff. and G. cf. decipiens (Fig. 18: 4a, b; Fig. 19: 5a, b) show already the more compressed and involute morphology of Graphoceras (Howarth 2013), whereas in all other features it is still very close to Brasilia. Graphoceras aff. magnum (Fig. 20: 1a, b) and G. cf. cavatum (Fig. 20: 2a, b) show the broad whorls of Brasilia, but the ribbing style of primitive Graphoceras. The bulk of the ammonites belong to the genus Graphoceras. Besides G. cf. concavum (Fig. 16: 1, 4; Fig. 15: 1a, b) the poorly sculptured G. cavatum (Fig. 13: 2a, b, 9a, b; Fig. 18: 2; Fig. 21: 2a, b) and G. cf. cavatum (Fig. 21: 1a, b) are typical. Graphoceras with more sculptured flanks are assigned to G. decorum (Fig. 15: 2; Fig. 22: 1a, b), G. aff. apertum (Fig. 15: 3a, b), G. pulchum (Fig. 15: 5a, b; Fig. 22: 3a, b), G. cf. pulchrum (Fig. 15: 4a, b), G. cf. v-scriptum (Fig. 18: 3) and G. formosum (Fig. 22: 2a, b, 5a, b), respectively. The strongest sculptured Graphoceras belong to G. fallax (Fig. 18: 5; Fig. 22: 4), G. aff. fallax (Fig. 13: 3) and G. cf. caduciferum (Fig. 17: 1a, b).

We here follow Chandler (1997) in the determination of the microconchs and assign these to Ludwigella. They show often specifically distinguished morphologies (Buckman 1887–1907; Contini 1969; Chandler 1997) ranging from nearly smooth to strongly ribbed morphotypes: Ludwigella tenuis (Fig. 13: 4), L. attenuata (Fig. 13: 6), L. arcitenens (Fig. 16: 3a, b; Fig. 15: 6a, b; Fig. 17: 3), L. cornu (Fig. 19: 2) L. aff. tenuis (Fig. 13: 5), L. sp. (Fig. 17: 5), L. micra (Fig. 19: 4), and L. attracta (Fig. 13: 7, 8; Fig. 19: 3).

4.2.2 Family Hammatoceratidae Buckman, 1887, Subfamily Hammatoceratinae Buckman, 1887

A single record from the Inopernabank (Fig. 14: 1a–c) resembles in its nucleus Bredyia diadematoides (Mayer) as figured by Rieber (1963) from Kappishäusern near Metzingen (Rieber 1963); however, its body chamber recalls the slightly more evolute Planammatoceras planiforme Buckman (typical of the Lower and lower Upper Aalenian; Kovács 2009; Sandoval et al. 2020) or Pl. lepsiusi (Gemmellaro). Due to the combination of these characters we here determined this ammonite as Planammatoceras sp. Most of the few hammatoceratids from the cavatum biohorizon of the Concavum Subzone in the studied sections are rather large, with smooth, high-oval outer whorls, very complex suture lines and a narrow umbilicus on the inner whorls (Fig. 14: 2a, b; Fig. 17: 4). The best match in literature we could find is with Euaptetoceras infernense sensu Buckman. The original type series of E. infernense (Roman) consists of small nuclei, which are very similar to the innermost whorls of the ammonite figured on Fig. 14: 2a, b. A more evolute variant is E. cf. kochi (Prinz) (Fig. 24: 1a, b). There is a striking homoeomorphy of this specimen with Brasilia decipiformis or Sonninia carinodiscus (Quenstedt [LT: Sonninia sowerbyi carinodiscus Quenstedt, 1886, p. 502, pl. 63, Fig. 3]). A fragmentary E. cf. euaptetum (Fig. 23: 1a–c) recalls in its habitus already the slightly younger E. amplectens; however, the umbilicus of the latter is more involute. These smooth, large-sized hammatoceratids already resemble their presumed descendants, the Early Bajocian Fissilobiceras ovale (Quenstedt). A nearly complete compressed specimen from bed 49 of the Heiligenbach section (SMNS 70602) belongs to the genus Euaptetoceras as well; however, due to its bad preservation a specific determination is impossible.

5.1.1 Opalinum Zone

Pygmaea-pumila faunal assemblage (Franz et al. 2018; samples He19-1–12)

The ostracod assemblage consists of 360 individuals (average of 30 individuals per sample) representing 34 species. The assemblage is characterized by Praeschuleridea ventriosa, Aphelocythere pygmaea, Metacytheropteron opalinum, Acrocythere pumila, Eucytherura transversiplicata, Euc. michelseni, Cardobairdia tesakovae, Eucytherura sp. 1 Franz et al., Euc. sp. 3 Franz et al., and Cytheropterina cribra.

The zonal index species Aphelocythere kuhni (Ohmert 2004) is missing in our samples. Stratigraphically important are Metacytheropteron opalinum, Cardobardia tesakovae, Eucytherura plumhoffi, Euc. foveolata sp. nov. and Procytherura euglyphea in addition to the nominal species of this community. The very rare Procytherura celtica as well as Gen. et sp. indet. 3 and Gen. et sp. indet. 4 (Franz et al. 2018) have also only been found in the Opalinum Zone. A range chart is given in Appendix 1.

In samples He19-7–12, eight species have their last occurrences in this faunal assemblage: Acrocythere pumila, Procytherura euglyphea, Eucytherura plumhoffi, Ostracode A Ballent, Eucytherura foveolata, Cardobairdia tesakovae, Metacytheropteron opalinum, and Eucytherura sp. 1 Franz et al.

5.1.2 “Comptum” Subzone (samples He19-13–14)

The stratigraphical significance of the ostracod assemblage from the “Comptum” Subzone is rather limited (8 species, represented by only 65 specimens). The assemblage is characterized by the extinction of the previously typical species Aphelocythere pygmaea, Acrocythere pumila, Procytherura euglyphea, Proc. celtica, Eucytherura plumhoffi, Euc. foveolata, Euc. sp. 1 Franz et al., Metacytheropteron opalinum, and Cardobairdia tesakovae. Aphelocythere pygmaea has its last appearance (very rare) in the claystones directly above the Comptumbank. Only Cytherella apostolescui appears for the first time, like in the Geisingen clay pit (Franz et al. 2018); the newly appearing species Praeschuleridea punctulata, Kinkelinella (K.) fischeri, Kinkelinella sp. 2 and Ektyphocythere aff. anterocosta are already known from older strata in Geisingen and some other sections.

Dominant species include Praeschuleridea ventriosa, Pr. punctulata and Kinkelinella (K.) fischeri.

5.1.3 Murchisonae Zone (samples He19-15–16)

The samples from the clays above the “Doppelbank” 20 + 21 yielded 126 specimens of 17 species, 12 of which were found in single specimens. Dominant species are Praeschuleridea ventriosa, Pr. punctulata and Homocytheridea sp. 1. Nine species are new; most important are Homocytheridea sp. 1, Bythoceratina (Praebythoceratina) sp. 1, Eucytherura sp. 3 Franz et al. and, to a minor degree, the very rare Pleurocythere sp. 1. The still undescribed Gen. et sp. indet. 10 Franz has its last appearance. Homocytheridea sp. 2, Procytherura aff. serangodes, Aphelocythere cf. pygmaea, Pleurocythere sp. 1 and Gen. et sp. indet. 12 were found only in single specimens in this assemblage.

Homocytheridea sp. 1 differs from Homocytheridea cf. punctulata from the Concavum Zone in the Geisingen clay pit. The stratigraphic distribution of Homocytheridea in the Upper Aalenian can be clarified only after investigation of further material.

5.1.4 Bradfordensis Zone, Bradfordensis Subzone (sample He19-17)

In this sample, we found 12 species (only 25 specimens), the majority of which are again represented by single specimens. Among the newly appearing species the solely abundant Progonocythere scutula (13 specimens) is particularly noteworthy. It was first described by Franz et al. (2018) from the Geisingen-Oolith (Gigantea Subzone). Progonocythere scutula and Gen. et sp. 9 Tesakova were observed in this sample only. A stratigraphical interpretation is not possible so far.

5.1.5 Bradfordensis Zone, Gigantea Subzone (samples He19-18–21)

The stratigraphical significance of this assemblage (35 species, represented by 169 specimens) is restricted. Eighteen species occur for the first time respectively reoccur in this part of the section: Praeschuleridea ornata, Pr. ventriosa, Balowella catena, Cytherelloidea lordi, Pleurocythere kirtonensis and rare Kinkelinella levata and Eocytheridea elongata in the uppermost sample. Dominant species are Praeschuleridea ornata and Pr. ventriosa, which alone account for > 22% of the total assemblage, Cytheropterina bicuneata, Praeschuleridea punctulata and Balowella catena. Eucytherura michelseni, Eucyth. sp. 3 Franz et al., Cytherelloidea cf. catenulata and Gen. et sp. indet. 9 have their last appearances in this section. Cytherelloidea lordi, Pleurocythere kirtonensis, Aaleniella compressa and Eucytherura sp. 5 Franz were found in this assemblage only.

As already observed in Geisingen (Franz et al. 2018) and Thanheim (Dietze et al. 2018), Kinkelinella levata – contrary to Ohmert (2004) – already occurs in the Bradfordensis Zone. The lower boundary of the Levata ostracod zone must therefore be significantly shifted downwards.

5.1.6 Concavum Zone (samples He19-21–28, Mue19-1, Ha19-1–3, Ro19-3–5)

The Concavum-Zone comprises the claystones immediately below and above the Inopernabank up to the Sowerbyi-Oolith. Since the claystones above the Rostrote Kalkbank are not exposed along the Heiligenbach creek, their basal part was sampled at the Mühlbächle creek in Jungingen and, for comparison purposes, at the Roschbach in Balingen-Zillhausen. The 14 samples obtained there show ostracod (and foraminifers) assemblages relatively rich in species and individuals. The upper half of these claystones and the basal Wedelsandstein Formation were sampled in the Hausterberg section. The claystones in this level are fine sandy and very poor in microfossils. In some samples only one foraminiferal and one ostracod species were found in small (foram.) to very small (ostr.) numbers.

This assemblage (including the samples from the Roschbach valley) comprises 2,365 specimens from 58 species, 34 of which appear for the first time in this section. Dominant species are Cytherella apostolescui, Praeschuleridea ornata and the newly appearing Eocytheridea lacunosa and Camptocythere pusilla. The still persisting Praeschuleridea ventriosa, Pr. punctulata, Balowella catena, Cytheropterina bicuneata, Eucytherura eberti and Bythoceratina (Praebyth.) sp. 1 are common as well. Of 34 species appearing here for the first time, the following ones are somewhat more common and useful for stratigraphic purposes (in the order of their first occurrence in this section): Eocytheridea lacunosa, Plumhofficythere clavatoides, Kinkelinella (Kink.) adunca, Camptocythere pusilla, Pleurocythere ohmerti, Kinkelinella (Kink.) sp. B Ohmert, Cytheropterina crassicostata, Cyth. alacostata, Kinkelinella (Kink.) cf. sermoisensis, Praeschuleridea cf. subtrigona, and Minyocythere tuberculata.

The two species of Cytheropterina are very conspicuous, but Cytheropterina alacostata is often represented by very small specimens.

Camptocythere pusilla, the index species of the Pusilla Ostracod Zone (Ohmert 2004), has been found here in large numbers. The very noticeable Plumhofficythere clavatoides, which also occurs in Northern Germany (Plumhoff 1963; Luppold 2003) and England (Bate 1963b), is obviously limited to the Bradfordensis Zone (Gigantea subzone) and Concavum Zone and would therefore also have stratigraphic significance.

Eucytherura eberti sp. nov., which has been found in rare specimens from the uppermost Opalinum Zone upwards, has its acme at this level. A number of further, mostly small species appear here for the first time. Although they are partly very conspicuous (e.g., ? Cytheropteron sp. 1, Eucytherura sp. 10), they are rather unsuitable for stratigraphic purposes due to their scarcity. Additionally, some of these rare species occur earlier elsewhere. A range chart for the Achdorf Formation is given in Appendix 2.

Bajocian

5.1.7 Discites Zone (samples Ha19-4–6)

The appearance of Kinkelinella (Ekt.) triangula and Progonocythere triangulata, together with Cytherelloidea cf. cadomensis and rare Fuhrbergiella horrida bicostata in this assemblage (374 specimens) clearly indicates the base of the Triangula Ostracod Zone, Triangulata Ostracod Subzone (= Discites Zone; Ohmert 2004). All other of the 15 species persist from the Aalenian. Praeschuleridea ornata, Progonocythere triangulata, Cytherella apostolescui and Cytherelloidea cf. cadomensis are dominant. Nine of the 15 species, including the dominant and the zonal index species, were also found at this level in the Thanheim section (Dietze et al. 2019). In contrast to Ohmert (2004), Kinkelinella (Ekt.) triangula appears in the Hausterberg section directly at the base of the Lower Bajocian.

Aalenian

5.2.1 Opalinum Zone

Opalinum and “Comptum” subzones: The strata of the Opalinum Zone were not in the focus of this investigation. However, the Opalinum Subzone reaches at least up to the “Wasserfallschichten” in the area. About 8 m above the “Zopfplatten” of the Heiligenbach section the “Comptum” Subzone is verified by numerous small-sized ammonites of the L. “comptum” – L. evolutum group.

5.5.2 Murchisonae Zone

At present, we cannot confirm strata of this age with ammonites.

5.2.3 Bradfordensis Zone

Bradfordensis Subzone: Beds 20–22 in the Roschbach section and bed 2 of the Mühlbächle section belong to the Bradfordensis Subzone. Ammonites are Brasilia bradfordensis and Staufenia staufensis.

Gigantea Subzone: For the moment, we place the ammonite fauna of the Inopernabank bed into the uppermost Gigantea Subzone. The graphoceratid fauna of this bed itself is not diagnostic enough to decide definitely, if this bed should be placed in the youngest Gigantea Subzone (younger than decipiformis biohorizon) or in the oldest Concavum Subzone (older than cavatum biohorizon). However, the single Planammatoceras sp. is very close to some of the hammatoceratids from the decipiformis biohorizon (Gigantea Subzone) of Geisingen, but very different from the hammatoceratids of the cavatum biohorizon (Concavum Subzone). Hence, we tentatively assign these beds in the Gigantea Subzone. Ammonites: Brasilia decipiens, Graphoceras cavatum, G. cf. caduciferum, G. aff. fallax, Ludwigella tenuis, L. aff. tenuis, L. attenuata, L. attracta, Planammatoceras sp.

5.2.4 Concavum Zone

Concavum Subzone (cavatum horizon): The Calceolabank (Roschbach: Bed 28, Mühlbächle: Bed 14, Heiligenbach: Bed 45, Hanneswiesle: Bed 4) belongs to the cavatum biohorizon of the Concavum Subzone. The fauna is a mixture of Brasilia spp., the dominant Graphoceras spp. and transitional morphologies besides Euaptetoceras infernense sensu Buckman. Ammonites: Brasilia decipiens, B. cf. decipiens, B. aff. decipiens, B. cf. decipiformis, Graphoceras cavatum, G. cf. cavatum, G. cf. concavum, G. fallax, G. aff. magnum, G. decorum, G. pulchrum, G. formosum, Ludwigella arcitenens, L. attracta, L. micra, L. cornu, Euaptetoceras cf. euaptetum, E. infernense sensu Buckman, E. cf. kochi.

Formosum Subzone: There is no evidence for this subzone in the Zollernalb.

Bajocian

5.2.5 Discites Zone

The Sowerbyi-Oolith bed belongs to the Discites Zone (see Dietze et al. 2019).

As Plumhoff (1963: 59) already stated, species of the genera Cytherella and Cytherelloidea dominate in the Upper Aalenian of the Swabian Alb, while they are absent in NW Germany in sediments of the same age. Nevertheless, the correlation succeeds by means of the genera and species occurring at different frequencies in both parts of the basin as listed in Plumhoff (1963: 59). Additionally, Plumhofficythere clavatoides Luppold (= Cytheridae, n. gen. sp. nov. 1 in Plumhoff 1963) is now also known from several sections in SW Germany.

In the present study and in the Geisingen section, a total of 33 genera and species were identified which are also known from the English, Scottish and Irish Aalenian and Lower Bajocian. Cytherella apostolescui, Cytherelloidea catenulata, Cyth. lordi, Cytheropterina cribra, Eocytheridea elongata, Eoc. lacunosa, Eucytherura liassica, Euc. michelseni, Euc. transversiplicata, Kinkelinella (Ekt.) triangula, Macrocypris aequabilis, M. liassica, Procytherura celtica, Proc. euglyphea, Proc. multicostata, and many others indicate a marine connection between these two sedimentary basins across the Paris Basin.

6.1.1 Opalinum Zone

Of the 34 species detected in the Heiligenbach section in the upper part of the Opalinuston Formation, 21 species are restricted to the Opalinum Zone or occur here for the last time. In accordance with the Geisingen clay pit (Franz et al. 2018), these are, in the order of their first occurrence: Aphelocythere pygmaea, Acrocythere pumila, Eucytherura plumhoffi, Eucytherura sp. 1 Franz et al., Gen. et sp. indet. 3 Franz et al., Eucytherura foveolata sp. nov., Cardobairdia tesakovae, Metacytheropteron opalinum, Gen. et sp. indet. 4 Franz et al., Procytherura sp. 2 Franz et al., and Procytherura celtica.

The ostracod assemblage of the upper Opalinuston Formation, Zillhausen Subformation (Franz and Nitsch 2009) can be well correlated with neighbouring regions. Although the zonal index Aphelocythere kuhni is missing here, Aphelocythere pygmaea, Acrocythere pumila and Metacytheropteron opalinum are also indicative for the upper Opalinum Zone in the Western and Middle Swabian Alb (Dilger 1963; Franz et al. 2018), Northern Germany and Northern Switzerland – there additionally Eucytherura plumhoffi and Cardobairdia tesakovae.

6.1.2 Opalinum Zone (“Comptum” Subzone) to Murchisonae Zone

The stratigraphically insignificant ostracod faunal assemblage of the “Comptum” Subzone and Murchisonae Zone has little in common with previously studied sections of the Swabian Alb. According to Dilger (1963), only Cytherella apostolescui and Cytheropterina bicuneata are common in this section. Besides these two species Franz et al. (2018) mentioned also Praeschuleridea punctulata and Kinkelinella fischeri. The composition of the ostracod assemblage in northern Germany is very different. According to Ainsworth (1986), Cytherella apostolescui is already present in the Toarcian of the Fastnet Basin (off Ireland).

6.1.3 Bradfordensis Zone

The ostracod assemblage of this part of the section shows good accordance with that of the Geisingen section with 15 common species. In contrast, the similarities with Dilger (1963) are limited to Aphelocythere dilgeri and Cytherelloidea lordi.

Progonocythere scutula, first described from the Geisingen Oolite (Gigantea Subzone; Franz et al. 2018: 78), occurs in the Heiligenbach section only in sample 17 (below the Staufensisbank), which presumably corresponds to the Bradfordensis Subzone. Due to the rarity of this species, a further stratigraphic interpretation is not possible.

The samples following higher up yielded Balowella catena, an index species of the Ohmerti-catena assemblage (Franz et al. 2018: 82). The second index species, Pleurocythere ohmerti, occurs here only above the Konglomeratbank, in the Concavum Zone.

6.1.4 Concavum Zone

Ohmert (2004) placed an ostracod assemblage with Kinkelinella (Kink.) levata, Aphelocythere recta and Pleurocythere cf. kirtonensis (= Pleurocythere ohmerti) from beds of the lower Discites Zone in the Pusilla ostracod zone (Concavum to Discites zones). The index species and additionally Plumhofficythere clavatoides, Cytheropterina alacostata and C. crassicostata, occur in the Zollernalb already in the Concavum Zone; Kinkelinella (Kink.) levata sporadically even in the uppermost Gigantea Subzone of the Bradfordensis Zone. Dilger (1963), who had summarized the interval from the Staufensisbank to the Sowerbyi-Oolith, also mentioned Camptocythere pusilla from the Balingen section (Zollernalb).

Apart from the zonal index species Camptocythere pusilla, Plumhofficythere clavatoides (Cytheridae, n. gen. sp. nov. 1 Plumhoff) is restricted to the Concavum Zone in northern Germany (Plumhoff 1963: 55). The latter occurs very rarely already in the Gigantea Subzone in Geisingen (Franz et al. 2018).

Reisdorf et al. (2016) and Tesakova (2017) did not mention any of the characteristic species of the Concavum Zone, which is a very thin interval in Northern Switzerland.

Herein we focus on the ammonites from the Inopernabank up to the Rostrote Kalkbank.

SW Germany: From the few data available it is most likely that the ammonites from the Inopernabank and the Rostrote Kalkbank are slightly younger compared to the ammonites from the decipiformis biohorizon of Geisingen (westernmost Swabian Alb). The few Graphoceras specimens from the Inopernabank are slightly more depressed and more involute compared to the “Graphoceras-morphology” of B. decipiformis (in a chronospecific sense as described in Dietze et al. 2014). Furthermore, Euaptetoceras infernense sensu Buckman – typical of the Concavum Subzone (Chandler and Sole 1996) – is unknown from the decipiformis biohorizon at Geisingen, where the highly variable Bredyia diadematoides and Planammatoceras spp. are the most common hammatoceratids; the latter was also recorded in the Inopernabank. Very close in depositional age to the Inopernabank and to the Calceolabank is the “Concava-Bank” around Metzingen and Kappishäusern (Middle Swabian Alb) (Rieber 1963). However, these outcrops and their ammonite content is still under investigation. Possibly the sections around Metzingen and Kappishäusern are slightly condensed.

The cavatum biohorizon (index species: Graphoceras cavatum; Calceolabank and Rostrote Kalkbank) is younger compared to the decipiformis biohorizon of Geisingen (Dietze et al. 2014) and younger than the ammonite faunas from the underlying Inopernabank and Konglomeratbank. The decipiformis biohorizon is characterised by smooth, large-sized Brasilia decipiformis, which occur only rarely in the cavatum biohorizon. The Brasilia fauna of the cavatum biohorizon consists of specimens with a smaller size, sometimes already showing the ribbing style of Graphoceras. The morphogenus Graphoceras is much more common in the cavatum biohorizon than in the decipiformis biohorizon, where most of the specimens belonging to the morphogenus Graphoceras are also less depressed. Variants of Bredyia diadematoides are abundant in the decipiformis biohorizon and not recorded in the cavatum biohorizon, where Euaptetoceras infernense sensu Buckman is common.

Ammonites of the Formosum Subzone occur in the “Bunte Mergel” and “Tonhorizont E1” of Ringsheim (Upper Rhine Valley) and in the Konglomeratbank/basal part of the Sowerbyi-Oolith near Achdorf (Wutach area). However, these beds are not yet subdivided into biohorizons.

SW England: The decipiens biohorizon (Bradfordensis Zone, Gigantea Subzone) is slightly older than the cavatum biohorizon of SW Germany, because therein occur Graphoceras and large-sized Brasilia (up to 0.4 m in diameter) in roughly equal numbers (Chandler 1997). The herein described cavatum biohorizon can be correlated with the cavatum biohorizon (Concavum Zone) of Dorset (Chandler 1997).